Pneumatic tool lubricant



Patented Nov. 20, 1945 PNEUMATIC TOOL LUBRICANT Donald L. Wright,Westfleld, N. J., assignor to Standard Oil Development Company, acorporation of Delaware No Drawing. Application September 15, 1943,Serial No. 502,461

7 Claims.

This invention relates to a new and improved lubricant for pneumatictools, such as percussion type drills and similar high speed compressedair machines and steam machines. More particularly, this inventionrelates to a lubricating composition comprising mainly a viscoushydrocarbon oil blended with minor proportions of a nondrying thickenedfatty oil and of a high molecular weight linear organicoxygen-containing polymer for providing eflicient lubrication tosurfaces of fast moving machine parts and to their guides, such asrapidly reciprocating pistons and their cylinder walls, the lubricant onsuch surfaces bein exposed during the machine operation to erosiveaction by forceful streams of gases and condensate which accompany theuse of gases like compressed air or steam.

Pneumatic tools present peculiar problems in lubrication. In general,they are rugged portable machines subjected to rough handling. Althoughthey need constant and eflicient lubrication at all times, they cannotbe equipped very easily with automatic lubricant feeding systems whichare delicate or which have large supply reservoirs.

Added difllculties in lubricating these machines arise from the rapidjarring movements of, and high gas velocities against lubricated parts,since these mechanical actions tend to separate the lubricant from themetal surfaces. Variations of temperatures occur in difierent parts ofthese machines. Gas expansion causes intense cooling in the surroundingparts and condensation of water vapor present in the usual gaseous orpneumatic fluids, compressed air and steam, while impacts and frictioncause relatively intense heating in other parts. Moisture condensed froma pneumatic fluid in the machine tends to wash away a film of lubricantnon-resistant to this action, and temperature variations afiect thefluidity of lubricants which have viscosities sensitive to thesevariations. When used outdoors and in mines, these machines are subjectto environmental temperatures which intensify these temperaturevariations, Lubricants are undesirable if they flow too freely over theheated parts of the tool, also, if they have sufflciently high viscosityin contact with the heated parts but congeal in contact with coolerparts or in the lubricator.

Materials have been compounded in the past to make lubricants havingadvantageous properties in one respect or another, but lubricants withthe desired combinations of qualities, particularly those ofadhesiveness and moisture resistance have not been available. In myprior Patent 2,228,429, I have disclosed and claimed a pneumatic toollubricant which satisfies the above requirements, but the presentinvention is a still further improvement over said prior element.

An object of the present invention is to prochurned to a foamy mass, 6,ability to resist moisture and adhere to metallic surfaces even whenemulsified, and 7, other qualities determined by speciflc requirementsof the service.

In accordance with the objects of this invention, an improvedlubrication of pneumatic tools is obtained by a composition which isable to give a lubricating film protection on working parts under rapidmechanical action regardless of moisture deposition.

Broadly, this invention involves the blending of a viscose hydrocarbonoil, such as a petroleum lubricating oil fraction, with a non-dryingviscous oxidized or thickened fatty oil and with a small amount of anoxygen-containing high molecular weight polymer which normally issubstantially solid. By a proper selection and proportioning of theseingredients, a blend can be obtained having suitable viscosity and pourpoint characteristics to assure proper flowing and penetration and whichprotectively stays on rubbing surfaces under severe operatingconditions.

Preferably, the principal ingredientsof blends found to have wideadaptability for use in many kinds of air driven percussion type toolsincluding outdoor equipment during all seasons of the year are a minerallubricating oil having a viscosity in the range of about to 925 Sayboltseconds at 100 degrees F. and a pour point below about +10 F., anon-drying thickened fatty oil, and a semi-solid to solid adhesive highmolecular weight polymer. As the mineral oil ingredient, a lubricatingoil fraction from a naphthenic crude, such as from a Colombian orCoastal crude, answers the purpose well, although, if desired, one mayuse lube oils derived from other types of crude, such as asphaltic,paramnic, mixed base, etc., provided they are selected or treated, as bydewaxing, etc., to have a suitable low pour point. Blown rape seed oilis particularly suitable as the non-drying thickened fatty oil.

Such additives include polymers of vinyl ethers having the generalformula B: H O=(!l-1i in which R1 is an unsubstituted or substitutedaliphatic, aromatic, or hydroaromatic radical, and R215 a hydrogen atomor a substituted or unsubstituted aliphatic radical, e. g., vinyl oleylether. vinyl isobutenyl ether, vinyl meta-cresyl ether, vinyl cyclohexylether, vinyl octadecyl ether, vinyl chloroethyl ether, vinyl aminopropyl ether, a-ethylvinyl isohexyl ether, a-chloromethyl vinyl laurylether, etc.; polymers of vinyl esters having me general formula(CH2=CR2OOC) n-Rl, in which R1 and R2 are as above and n is an integerhaving a value of 1 or more, e. g., vinyl stearate, vinyl ester of acidsobtained by oxidation of paraflln wax, vinyl chloropropionate, vinylaminopalmitate, vinyl adipate, vinyl citrate, etc. polymers of acrylicacid esters having the general formula, R'OOCC (X) =CH2, in which R isan unstituted or substituted aliphatic, aromatic, or h'ydroaromaticgroup, preferably containing at least carbon atoms, and X is a H or ahalogen atom, or a CH: group or a CzHs group, e. g., lauryl acrylate,cetyl acrylate, octadecyl acrylate, amylphenyl methacrylate, lsoheptylcyclohexyl chloroacrylate, chlorodecyl methacrylate, etc., especiallysuch polyacrylic esters having a molecular weight of 1,000 to 10,000,although polymers having higher molecular weights such as 20,000 or even50,000, or more may be used.

Another type of high molecular weight oxygencontaining substance whichcan b used for the purpose of this invention is the class ofcondensation products or polyesters of substituted fatty acids havingthe general formula in which R is a H atom or an unsubstituted orsubstituted aliphatic, aromatic, or hydroaromatic group, a: and it mayequal 0 or any integer provided that m+ll equals at least 5, and where nis 0 or an integer and m is a whole number and Z is a flmctional groupwhich has one replaceable hydrogen atom, Z being capable of esterifyinga carboxyl group. Some of these polyesters are described in U. 8. Patent2,147,647, and are typified by the polyester having a molecular weightof about 14,000 obtained by po yesterification of 12- hydroxy stearicacid in the presence of a small amount of adipic acid.

These various polymers range from viscous, tacky oils to tough, elastic,almost colorless, and substantially solid mass. Chemically, theseoxygen-containing polymers are characterized as highly saturated in thatthey have an iodine number below 20, preferably below 10, and frequentlybelow 1 or 2.

About 0.1 to 1.0% of this material is readily dissolved in the blend ofhydrocarbon oil and nondrying thickened fatty oil and when th'usdissolved forms a homogeneous mixture having a stable cohesiveness to beperceived in the formation of long strings or threads when the mixtureis pulled apart. This cohesiveness is stable to light, air, heat andmoisture.

Usually the percentage of thickened fatty oil should be in the range ofabout 1-15%, generally about 5-10% will be found most useful. Thelubricating oil base stock will, except for possible minor amounts ofaddition agents such as antioxidants, dyes, pour depressors, etc.,comprise the Viscosity of mineral oil (sec. Saybolt at F.) ercen 100 200300 800 Mineral oi (naphthenic base) 94. 7 92.5 94.7 89.0 Polymerizedlauryl methacrylate 0.3 0.5 0. 3 1.0 Blown rape seed oil 5. 0 7. 0 5.010.0

1 Average molecular weight about 10,000.

Each of these blends has a very satisfactory low pour point and a highviscosity index, which is the measurement of variation in viscosity withtemperature changes of the oil according to the procedure described inthe article by Dean and Davis, Chemical and Metallurgical Engineering,

vol. 36, 1929, page 618. These various blends are particularly suitablefor lubrication of pneumatic rock drills, Examples 2 and 3 beingintended primarily for use in temperate climates while Example l isespecially adapted for use in colder climates and Example 4 in hotterclimates.

'Although particular compositions with specific ingredients andproportions have been described, the invention is not limited thereto,The invention can also be carried out with other fatty oils of vegetableor animal origin having qualities similar to those of blown rape seedoil. Nondrying thickened fatty oils having high viscosities may beprepared from rape seed oil, cotton seed oil, maize oil, seal oil, andsperm oil by airblowing, or by other known methods of thickening, suchas catalytic or electrical polymerization which reduce the iodinenumbers of such oils to below 75. To prepare the ordinary connnercialnon-drying thickened fatty oils by air blowing, air is blown into anatural fatty oil with stirring for a period of about 15 to 30 hours ata temperature of about F. until the desired speciiiic gravity orviscosity of the thickened oil is reached. Rape seed oil, for example,would be treated in this manner until its specific gravity is raisedfrom about 0.914 to between about 0.968 and 0.990 as determined at 60 F.

The proportioning of the thickened fatty oil to themineral oil dependslargely upon the viscosities of these ingredients and the desiredviscosity for the blend, particularly when a pour depressant is used forultimately reducing the pour point of the blend. The mineral oil neednot be so restricted as to its source if the pour point of its blendwith the fatty oil is not required to be of the order obtained in thespecific examples. Lubricating oils with, flash points above the flashpoint of a gas oil from all types of crude oils may be used. Syntheticlubricating oils with low pour points may be used. Al though the minerallubricating oils are preferably'selected from naphthenic base crudes,some dewaxed parafflnic base oils may also be used. As anotheralternative modification of the high molecular weight oxygen-containinglinear type polymer, one may use copolymers, such as described in Patent2.l25,885, made by copolymerizing acrylic acid esters of two diilerentmonohydric aliphatic alcohols, for instance ethyl alpha methacrylate andlauryl alpha methacrylate, or the ethyl and mono octadecyl alphamethacrylates.

In using mineral oils having relatively higher pour points, a smallamount of synthetic pour point depressants may be added, particularlythose containing long alkyl group branches. These alkyl groups shouldhave preferably 10 to 30 carbon atoms in straight chains, andmay beJoined to other long alkyl groups or a cyclic group, preferably to apolycyclic group, e. g., a naphthyl or a naphthol group. The method ofsynthesizing these products is wellknown in the art and described in U.S. Patent No. 1,815,022, granted to G. H. B. Davis, July 14, 1931. Ingeneral, this method involves the reaction of chloroparafilns withoneanother or with aromatics, such as naphthalene, in the presence of aFriedel- Crafts type of catalyst, These pour point depressants in aconcentration of only about 0.5 to 3% lower the pour points ofcompositions described in the preceding examples by more than 5 F,

The description of the aforementioned'compositions as being particularlyintended for use in percussion air drills, in which specificrequirements may exist for low pour points, adhesive ness, and constancyof viscosity under widely varying temperature conditions, is notintended to limit the invention to such a specific use for tnesecompositions. Blends prepared in accordance with this invention areuseful for other purposes, such as Jackv hammers, stopers, drifters,

. wagon drills, chippers, tempers, riveters, pavement breakers. andsimilar mechanisms having high speed reciprocating pistons activated bycompressed air or steam. The present invention has several distinctadvantages over compositions prepared heretofore; one importantadvantage is that the high molecular weight linear typeoxygen-containing polymers, particularly the polymerized acrylic acidesters, have a tendency to emulsify to a greater extent than do thesimple high molecular weight Ease oi. emulsiflcation permits betteradherence oi the lubricant to the working surfaces 01 pneumatic toolswhere emulsion-producing moisture is generally present. therefore areduced consumption of the lubricant is eflected, Another advantage ofsuch oxygen-containing polymers is their relatively high resistance tomolecular weight breakdown, and consequent decrease of adhesivity andviscosity during use.

Lubricant compositions of this invention may be applied through any of.the systems of lubrication usuall employed with pneumatic tools. Handoiling is still common, but special line lubricators for injecting smallquantities into the air stream at a point about ten feet from the toolare increasing. Line lubrlcators assure lubrication without attentionover long periods. The compositions 01 this invention are stable andhomogeneous, being even superior in these respects to the lubricants ofmy prior patent.

Other ingredients may be added in minor amounts. as might be desired forfurther improving the lubricant, but such agents as sludge dispersers,oxidation inhibitors, corrosion inhibitors and oiliness agents are ingeneral unnecessary.

I do not desire to be limited to any given speclflc illustration of theinvention because there may be relatively wide variation in the kindsand hydrocarbon polymers such as polyisobutylene.

proportions of the materials used without departing from the broaderscope of the invention. I desire to be limited only by the followingclaims in which it is my intention to claim all novelty as broadly asthe prior art permits.

I claim:

1. A lubricant having a viscosity in the range of about 150 to 1000seconds Saybolt at 100 F. adapted for use in compressed air and steammotivated machines having high speed reciprocating pistons, whichcomprises a major proportion of a hydrocarbon lubricating oil and about1 to 15% of a non-drying thickened fatty oil and about 0.1 to 1.0%.01 alinear oxygen-containing polymer which normally"'ls"plastic to solid,has

an iodine number below 20 and a molecular weight of at least 1,000, saidpolymer being a polymer or an oxygen-containing organic compound havingthe group J=(/.liz. 2. A lubricant according'to claim 1 in which thepolymer is composed or only carbon, hydrogen and oxygen, and has amolecular weight oi'atleast 5,000.

3. A lubricant adapted for use in pneumatic tools which comprises about85 to 95% of a pctroleum lubricating oil having a viscosity in the rangeof about 100 to 950 Baybolt seconds at 100" F. and a maximum pour pointof +l0 F., about 0.1 to 0.5% of a normally semi-solid to solid acrylicacid ester polymer having a molecular weight oi at least 5,000 and asmall amount of a nonrying thickened fatty oil.

4. A pneumatic tool lubricant having a stable cohesiveness, goodemulsification tendencies, a maximum pour point below +10 F., aviscosity in the range of about 150 to 1000 Saybolt seconds at 100 l-".,and comprising in major proportion a petroleum lubricating oil having aviscosity in the range or about 100 to 950 Saybolt seconds at teristics,having a viscosity of about 400 to 600 1 seconds'saybolt at 100 F., amaximum pour point of about -10" R, and comprising in major proportion ahydrocarbon lubricating oil having a viscosity 0! about 200 to 400seconds Saybolt at 100 F., 1 to 15% of blown rape seed oil, and 0.1%

to 1.0% of acrylic acid ester polymer having a molecular weight of about5,000 to 50,000.

6. A compressed-air driven rock drill lubricant having a viscosityin therange of about 490 to 515 saybolt seconds at 100 F., a maximum pourpoint of-about. -25 F. and comprising about 92.7% of a naphthenic baselubricating oil having a viscosity in the range of about 300 to 315'Saybolt seconds at 100 F., about 7.0% or blown rape seed oil, and about0.2 to 0.5% of lauryl' alpha methacrylate polymer having a molecular ofa non-drying thickened iatty oll'ana about 0.1

to 1.0% of. a normally semi-solid to solid acrylic acid ester polymer.

- mm n warorrr.

